Changes in the Lectin Pathway Following Intracerebral or Spontaneous Subarachnoid Hemorrhage

Systemic Inflammation after Aneurysmal Subarachnoid Hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is one of the most severe neurological disorders, with a high mortality rate and severe disabling functional sequelae. Systemic inflammation following hemorrhagic stroke may play an important role in mediating intracranial and extracranial tissue damage. Previous studies showed that various systemic inflammatory biomarkers might be useful in predicting clinical outcomes. Anti-inflammatory treatment might be a promising therapeutic approach for improving the prognosis of patients with aSAH. This review summarizes the complicated interactions between the nervous system and the immune system.

Compartmental Cerebrospinal Fluid Events Occurring after Subarachnoid Hemorrhage: An "Heparin Oriented" Systematic Review

Subarachnoid hemorrhage (SAH) represents a severe acute event with high morbidity and mortality due to the development of early brain injury (EBI), secondary delayed cerebral ischemia (DCI), and shunt-related hydrocephalus. Secondary events (SSE) such as neuroinflammation, vasospasm, excitotoxicity, blood-brain barrier disruption, oxidative cascade, and neuronal apoptosis are related to DCI. Despite improvement in management strategies and therapeutic protocols, surviving patients frequently present neurological deficits with neurocognitive impairment. The aim of this paper is to offer to clinicians a practical review of the actually documented pathophysiological events following subarachnoid hemorrhage. To reach our goal we performed a literature review analyzing reported studies regarding the mediators involved in the pathophysiological events following SAH occurring in the cerebrospinal fluid (CSF) (hemoglobin degradation products, platelets, complement, cytokines, chemokines, leucocytes, endothelin-1, NO-synthase, osteopontin, matricellular proteins, blood-brain barrier disruption, microglia polarization). The cascade of pathophysiological events secondary to SAH is very complex and involves several interconnected, but also distinct pathways. The identification of single therapeutical targets or specific pharmacological agents may be a limited strategy able to block only selective pathophysiological paths, but not the global evolution of SAH-related events. We report furthermore on the role of heparin in SAH management and discuss the rationale for use of intrathecal heparin as a pleiotropic therapeutical agent. The combination of the anticoagulant effect and the ability to interfere with SSE theoretically make heparin a very interesting molecule for SAH management.

MASP-2 and MASP-3 inhibitors block complement activation, inflammation, and microvascular stasis in a murine model of vaso-occlusion in sickle cell disease

Patients with sickle cell disease (SCD) have ongoing hemolysis that promotes endothelial injury, complement activation, inflammation, vaso-occlusion, ischemia-reperfusion pathophysiology, and pain. Complement activation markers are increased in SCD in steady-state and further increased during vaso-occlusive crisis (VOC). However, the mechanisms driving complement activation in SCD have not been completely elucidated. Ischemia-reperfusion and heme released from hemoglobin during hemolysis, events that characterize SCD pathophysiology, can activate the lectin pathway (LP) and alternative pathway (AP), respectively. Here we evaluated the role of LP and AP in Townes sickle (SS) mice using inhibitory monoclonal antibodies (mAb) to mannose binding lectin (MBL)-associated serine protease (MASP)-2 or MASP-3, respectively. Townes SS mice were pretreated with MASP-2 mAb, MASP-3 mAb, isotype control mAb, or PBS before they were challenged with hypoxia-reoxygenation or hemoglobin. Pretreatment of SS mice with MASP-2 or MASP-3 mAb, markedly reduced Bb fragments, C4d and C5a in plasma and complement deposition in the liver, kidneys, and lungs collected 4 hours after challenge compared to control mAb-treated mice. Consistent with complement inhibition, hepatic inflammation markers NF-ĸB phospho-p65, VCAM-1, ICAM-1, and E-selectin were significantly reduced in SS mice pretreated with MASP-2 or MASP-3 mAb. Importantly, MASP-2 or MASP-3 mAb pretreatment significantly inhibited microvascular stasis (vaso-occlusion) induced by hypoxia-reoxygenation or hemoglobin. These studies suggest that the LP and the AP are both playing a role in promoting inflammation and vaso-occlusion in SCD. Inhibiting complement activation via the LP or the AP might inhibit inflammation and prevent VOC in SCD patients.

TIPE2 attenuates neuroinflammation and brain injury through Bcl-2/Bax/cleaved caspase-3 apoptotic pathways after intracerebral hemorrhage in mice

BACKGROUND

Intracerebral hemorrhage (ICH) is a serious disease with high mortality and morbidity, and effective treatment is limited. A large amount of evidence suggests that the inflammatory response contributes to secondary brain damage following ICH. TIPE2 is an essential negative regulator of both innate and adaptive immunity, and depletion of TIPE2 causes inflammatory disease. However, the possible role of TIPE2 following ICH has not been reported.

METHODS

In this study, we investigated TIPE2 levels and inflammation in microglia treated with erythrocyte lysate in vitro. In addition, we analyzed the role of Bcl-2/Bax/cleaved caspase-3 apoptotic pathways in ICH mice. Furthermore, we observed proinflammatory cytokine production, BBB disruption, cerebral water content and neurological damage in ICH mice.

RESULTS

We found that TIPE2 levels were significantly decreased in erythrocyte lysate-treated microglia compared to control microglia.Upregulation of TIPE2 decreased microglia activation and cytokine production and accelerated brain damage in ICH mice. Furthermore, upregulation of TIPE2 decreased the higher ratio of Blc-2/Bax and increased cleaved caspase-3 levels in ICH mice. In addition, upregulation of TIPE2 attenuated proinflammatory cytokine production, BBB disruption, and severe brain inflammation after ICH.

CONCLUSION

These results demonstrated that TIPE2 was negatively correlated with the pathogenesis of ICH, which prevented brain injury and attenuated deleterious inflammatory responses following ICH. TIPE2 might serve as a novel target for ICH therapy.

Proteomics-Based Approach to Identify Novel Blood Biomarker Candidates for Differentiating Intracerebral Hemorrhage From Ischemic Stroke-A Pilot Study

Background: A reliable distinction between ischemic stroke (IS) and intracerebral hemorrhage (ICH) is required for diagnosis-specific treatment and effective secondary prevention in patients with stroke. However, in resource-limited settings brain imaging, which is the current diagnostic gold standard for this purpose, is not always available in time. Hence, an easily accessible and broadly applicable blood biomarker-based diagnostic test differing stroke subtypes would be desirable. Using an explorative proteomics approach, this pilot study aimed to identify novel blood biomarker candidates for distinguishing IS from ICH.

Material and Methods: Plasma samples from patients with IS and ICH were drawn during hospitalization and were analyzed by using liquid chromatography/mass spectrometry. Proteins were identified using the human reference proteome database UniProtKB, and label-free quantification (LFQ) data were further analyzed using bioinformatic tools.

Results: Plasma specimens of three patients with IS and four patients with ICH with a median National Institute of Health Stroke Scale (NIHSS) of 12 [interquartile range (IQR) 10.5–18.5] as well as serum samples from two healthy volunteers were analyzed. Among 495 identified protein groups, a total of 368 protein groups exhibited enough data points to be entered into quantitative analysis. Of the remaining 22 top-listed proteins, a significant difference between IS and ICH was found for Carboxypeptidase N subunit 2 (CPN2), Coagulation factor XII (FXII), Plasminogen, Mannan-binding lectin serine protease 1, Serum amyloid P-component, Paraoxonase 1, Carbonic anhydrase 1, Fibulin-1, and Granulins.

Discussion: In this exploratory proteomics-based pilot study, nine candidate biomarkers for differentiation of IS and ICH were identified. The proteins belong to the immune system, the coagulation cascade, and the apoptosis system, respectively. Further investigations in larger cohorts of patients with stroke using additional biochemical analysis methods, such as ELISA or Western Blotting are now necessary to validate these markers, and to characterize diagnostic accuracy with regard to the development of a point-of-care-system for use in resource-limited areas.

Neuroprotective Therapies for Spontaneous Intracerebral Hemorrhage

Patients who survive the initial ictus of spontaneous intracerebral hemorrhage (ICH) remain vulnerable to subsequent injury of the perilesional parenchyma by molecular and cellular responses to the hematoma. Secondary brain injury after ICH, which contributes to long-term functional impairment and mortality, has emerged as an attractive therapeutic target. This review summarizes preclinical and clinical evidence for neuroprotective therapies targeting secondary injury pathways following ICH. A focus on therapies with pleiotropic antiinflammatory effects that target thrombin-mediated chemotaxis and inflammatory cell migration has led to studies investigating statins, anticholinergics, sphingosine-1-phosphate receptor modulators, peroxisome proliferator activated receptor gamma agonists, and magnesium. Attempts to modulate ICH-induced blood-brain barrier breakdown and perihematomal edema formation has prompted studies of nonsteroidal antiinflammatory agents, matrix metalloproteinase inhibitors, and complement inhibitors. Iron chelators, such as deferoxamine and albumin, have been used to reduce the free radical injury that ensues from erythrocyte lysis. Stem cell transplantation has been assessed for its potential to enhance subacute neurogenesis and functional recovery. Despite promising preclinical results of numerous agents, their outcomes have not yet translated into positive clinical trials in patients with ICH. Further studies are necessary to improve our understanding of the molecular events that promote damage and inflammation of the perihematomal parenchyma after ICH. Elucidating the temporal and pathophysiologic features of this secondary brain injury could enhance the clinical efficacy of neuroprotective therapies for ICH.

Plasma neurofilament light chain is associated with mortality after spontaneous intracerebral hemorrhage

Background Neurofilament light chain (NfL) is a neuron-specific biomarker with prognostic ability in several types of central nervous system injuries. This study investigates if plasma NfL (pNfL) is elevated early after spontaneous intracerebral hemorrhage (ICH) and whether such elevation reflects disease severity and day-30 outcome. Methods pNfL was quantified by single molecule array analysis in 103 reference subjects (RS) and in samples from 37 patients with ICH obtained on admission to hospital and at 24-h follow-up. The primary outcome was day-30 mortality. Clinical status on admission was evaluated by standardized scoring systems. Results Median pNfL among RS was 9.6 (interquartile range [IQR] 6.2) pg/mL. Upon admission, ICH patients had pNfL of 19.8 (IQR 30.7) pg/mL increasing to 35.9 (IQR 44.5) pg/mL at 24 h (all, p < 0.001). On admission, pNfL was higher among ICH non-survivors than survivors (119.2 [IQR 152.6] pg/mL vs. 15.7 [IQR 19.6] pg/mL, p < 0.01) and this difference was observed also on 24 h follow-up (195.1 [IQR 73.9] pg/mL vs. 31.3 [IQR 27.8] pg/mL, p < 0.01). The area under the receiver operating characteristic curve (ROC AUC) for discrimination of day-30 mortality was significant on admission (AUC = 0.83, 95% confidence interval [CI]: 0.56-1.0) and increased on 24-h follow-up (AUC = 0.93, 95% CI: 0.84-1.0). The odds ratio (OR) for death, by each quartile increase in pNfL was significant both on admission (OR = 4.52, 95% CI: 1.32-15.48) and after 24-h follow-up (OR = 9.52, 95% CI: 1.26-71.74). Conclusions PNfL is associated with day-30 mortality after spontaneous ICH when early after the ictus.

Lectin complement pathway initiators after subarachnoid hemorrhage - an observational study

Background

This exploratory study investigated the time-course of lectin complement pathway (LCP) initiators in cerebrospinal fluid (CSF) and plasma in patients with subarachnoid hemorrhage (SAH), as well as their relationship to delayed cerebral ischemia (DCI) and functional outcome.

Methods

Concentrations of ficolin-1, ficolin-2, ficolin-3, and mannose-binding lectin (MBL) were analyzed in CSF and plasma from patients with SAH. Samples were collected daily from admission until day 9 (CSF; N__PATIENTS = 63, n__SAMPLES = 399) and day 8 (plasma; N__PATIENTS = 50, n__SAMPLES = 358), respectively. Twelve neurologically healthy patients undergoing spinal anesthesia and 12 healthy blood donors served as controls. The development of DCI during hospitalization and functional outcome at 3 months (modified Rankin Scale) were registered for patients.

Results

On admission, CSF levels of all LCP initiators were increased in SAH patients compared with healthy controls. Levels declined gradually over days in patients; however, a biphasic course was observed for ficolin-1. Increased CSF levels of all LCP initiators were associated with a poor functional outcome in univariate analyses. This relationship persisted for ficolin-1 and MBL in multivariate analysis after adjustments for confounders (age, sex, clinical severity, distribution and amount of blood on CT-imaging) and multiple testing (1.87 ng/mL higher in average, 95% CI, 1.17 to 2.99 and 1.69 ng/mL higher in average, 95% CI, 1.09 to 2.63, respectively). In patients who developed DCI compared with those without DCI, CSF levels of ficolin-1 and MBL tended to increase slightly more over time (p_interaction = 0.021 and 0.033, respectively); however, no association was found after adjustments for confounders and multiple testing (p-adj_interaction = 0.086 and 0.098, respectively). Plasma ficolin-1 and ficolin-3 were lower in SAH patients compared with healthy controls on all days. DCI and functional outcome were not associated with LCP initiator levels in plasma.

Conclusion

Patients with SAH displayed elevated CSF levels of ficolin-1, ficolin-2, ficolin-3, and MBL. Increased CSF levels of ficolin-1 and MBL were associated with a poor functional outcome.

Trial registration

This study was a retrospective analysis of samples, which had been prospectively sampled and stored in a biobank. Registered at clinicaltrials.gov (NCT01791257, February 13, 2013, and NCT02320539, December 19, 2014).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-020-01979-y.

Plasma Neurofilament Light Chain Is Associated with Poor Functional Outcome and Mortality Rate After Spontaneous Subarachnoid Hemorrhage

The initial clinical status after subarachnoid hemorrhage (SAH) is an important outcome predictor, but the mechanisms behind the early brain injury (EBI) remains incompletely understood. Elevated neurofilament levels in the cerebrospinal fluid at protracted stages after SAH are associated with poor outcome, but the potential association between plasma neurofilament (pNfL) levels during EBI, disease severity on admission, and poor outcome remains unaddressed. Plasma NfL (pNfL) was measured by single molecule array in 44 SAH patients on admission and 24 h after ictus, as well as in 44 controls. Disease severity on admission was assessed by validated scoring systems, and day 30 modified Rankin Scale (mRS) score was registered. Admission levels of pNfL correlated with clinical disease severity scores (rho = 0.43, p < 0.01 and rho = 0.48, p < 0.001) as well as day 30 mRS score (rho = 0.53, p < 0.001). Each quartile increase in pNfL was independently associated with poor functional status (mRS > 4) [odds ratio = 1.98, 95% confidence interval (CI): 1.01-3.88, p = 0.05]. Non-survivors had higher pNfL than survivors; on admission [17.6 pg/mL (IQR 11.4) vs. 8.4 pg/mL (IQR: 8.9), p < 0.01] and 24 h after ictus [29.9 pg/mL (IQR 90.4) vs 7.8 pg/mL (IQR 26.9), p = 0.01]. Each quartile increase in pNfL was independently associated with reduced survival rate [log-rank = 0.02, hazard ratio = 2.29 (95% CI): 1.15-4.57), p = 0.02]. PNfL levels are associated with disease severity during the EBI phase of SAH. Higher pNfL levels during EBI are associated with poor functional outcome on day 30 after ictus and increased mortality rate.

Neuroinflammation and Microvascular Dysfunction After Experimental Subarachnoid Hemorrhage: Emerging Components of Early Brain Injury Related to Outcome

Aneurysmal subarachnoid hemorrhage has a high mortality rate and, for those who survive this devastating injury, can lead to lifelong impairment. Clinical trials have demonstrated that cerebral vasospasm of larger extraparenchymal vessels is not the sole contributor to neurological outcome. Recently, the focus of intense investigation has turned to mechanisms of early brain injury that may play a larger role in outcome, including neuroinflammation and microvascular dysfunction. Extravasated blood after aneurysm rupture results in a robust inflammatory response characterized by activation of microglia, upregulation of cellular adhesion molecules, recruitment of peripheral immune cells, as well as impaired neurovascular coupling, disruption of the blood-brain barrier, and imbalances in endogenous vasodilators and vasoconstrictors. Each of these phenomena is either directly or indirectly associated with neuronal death and brain injury. Here, we review recent studies investigating these various mechanisms in experimental models of subarachnoid hemorrhage with special emphasis on neuroinflammation and its effect on microvascular dysfunction. We discuss the various therapeutic targets that have risen from these mechanistic studies and suggest the utility of a multi-targeted approach to preventing delayed injury and improving outcome after subarachnoid hemorrhage.